Just when you think it couldn’t get worse, I am afraid that researchers have more bad news.

NOTE: pick the correct link

Analyses of how the epidemic spread in China and on the Diamond Princess cruise ship are now being published and they suggest that about 35% of COVID-19 cases are spread by people with no symptoms of the disease.

This comes from two recent articles, one on temporal dynamics in viral shedding and transmissibility of the virus, and the other on estimates of the asymptomatic ratio of novel coronavirus infections.

This is problematic for many reasons.

For one thing, our testing protocols here in Hawaii require that a person get a doctor’s order before they can be tested. The usual reason a doctor will give an order is if a person has a cough and/or fever. So, this means that we are missing 35% of contagious people.

Another reason this is bad is that it makes it much harder for us to know who to home-quarantine and require to wear face masks. Right now we emphasize that people with symptoms must stay at home and wear face masks when around other people.

The Diamond Princess in Bali in 2016. New research is out on the spread of COVID-19 on the ship. Flickr: Ya, saya inBaliTimur

But it is looking more and more like the only successful quarantine strategy will be to keep everyone at home for a few weeks — like they did in Wuhan and are doing now in Italy and San Francisco.

The third reason this is bad is that it makes it hard to know who to stay away from.

When you go to the grocery store at 6 a.m. to avoid the crowds, you can no longer just stay away from people who are coughing or look sick, you have to stay away from everyone. Until more testing on asymptomatic people is done to find the ones who need to be quarantined, we will just have to assume that everyone has the virus!

And fourth, it makes it impossible for us to know when we are contagious ourselves and capable of passing the virus on to all of our contacts. How terrible it would feel to know that we gave the virus to someone we love.

This pattern of asymptomatic transmission is similar to the flu and is one of the main reasons we cannot eradicate the flu. In contrast, the SARS virus in 2003 could only be transmitted by symptomatic people and thus was fairly quickly eradicated.

It should be noted that both of the studies I cited for this piece have not been peer reviewed yet. They are papers that have been submitted for peer review and are being made available on the website medRxiv.com because of the critical need for information on this new virus.

According to its website, medRxiv “was founded by Cold Spring Harbor Laboratory, a not-for-profit research and educational institution, Yale University, and BMJ, a global healthcare knowledge provider.”

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About the Author

  • Matt Binder
    Matt Binder was a science and medicine reporter in the 1980s and 1990s and produced two documentaries about the AIDS epidemic and nine documentaries about the social impacts of the genetic revolution. He was, until the coronavirus crisis, an after-school science teacher at Waimea Middle School.